From Chicago to Boston to Washington, D.C., folks were treated to up to a foot (0.3 meters) of snow, with windchill dipping into the negative digits. So far, nine deaths have been blamed on the storm.

Long Island, New York, and parts of coastal Massachusetts experienced blizzard conditions, said Chris Vaccaro, a spokesperson with the National Weather Service. Other parts of the country suffered under a nor'easter.

Nor'easters are simply storms that affect the northeastern part of the U.S., move in a northeasterly direction, and produce winds coming from the northeast. "That's the trifecta," said Vaccaro.

In the months of October or November, they can produce rain, while in January or February, they can produce snow.

They differ from blizzards in that—according to the National Weather Service—blizzards involve large amounts of snow, winds in excess of 35 miles (56 kilometers) an hour, and visibilities of less than a quarter mile (half a kilometer).

Visibility is the most important element in the mix, said meteorologist Matt Kelsch, with the University Corporation for Atmospheric Research, in an interview last year. "Usually, it takes that strength of wind—[35 miles (56 kilometers) an hour]—to pick enough snow off the ground to reduce visibility that much," he said.

"[But] it doesn't always have to be snowing to be a blizzard," Kelsch added. In the U.S., areas of the Great Plains and western states can get something called "ground blizzards": storms in which high winds pick up snow from the ground and whip it around, greatly reducing visibility.

Will blizzards become more frequent in the future as a result of climate change? That's difficult to know for sure, said Kelsch, but warming oceans may increase the contrast between warm coastal air and cooler air over land, which could increase the frequency of storms.

"Weather and climate are directly connected. You can't change one and not expect an effect on the other," Kelsch said.